Ketone peroxide compositions

ABSTRACT

Safe ketone peroxide compositions are provided utilizing a novel solvent system which boils smoothly over a wide range of temperatures.

REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 396,524 filedSept. 12, 1973 (now U.S. Pat. No. 3,957,884).

FIELD OF INVENTION

The present invention is directed to ketone peroxide compositions,particularly "safe" ketone peroxide compositions.

BACKGROUND TO THE INVENTION

Ketone peroxides are extensively used for the initiation ofpolymerization of ethylenically unsaturated compounds. Peroxides,however, have a tendency to be inflammable and explosive, with someexhibiting these properties to a greater extent than others. Theseproperties carry with them obvious hazards to the users of the materialsas well as to the manufacturers.

Many suggestions have been made to reduce the inflammability of ketoneperoxides usually involving the incorporation of large quantities ofwater in the composition, the use of various additives and the use ofparticular solvents.

One typical prior art suggestion to provide safe ketone compositions isdescribed in U.S. Pat. No. 3,330,871, wherein it is indicated that aclass of "Safety Solvents" for for ketone peroxide may be used toprovide compositions which exhibit resistance to ignition and onceignited burn mildly. A wide variety of solvents is mentioned includingvarious glycols. However, it has been found that, while the compositionsprovided in the manner disclosed in this patent do indeed exhibit someresistance to ignition and once ignited burn mildly, after burning for aperiod of time, which may vary widely depending on the solvent used andthe quantity present, the composition suddenly flares up and burnsvigourously. The tendency of these prior art compositions to flare upsuddenly is extremely hazardous to a user or manufacturer seeking toextinguish the ignited composition, since while the ignited compositionmay be burning mildly and the operator can approach the flame withsuitable extinguishing equipment, before extinguishing the flame, asudden flare up may occur, causing injury to the operator.

SUMMARY AND GENERAL DESCRIPTION OF INVENTION

The present invention provides a safe acyclic ketone peroxidecomposition which exhibits considerable resistance to ignition and whenignited burns in a controlled manner until all the peroxide compositionhas been consumed. Thus, the present invention avoids the flare upproblem attendant the prior art compositions of U.S. Pat. No. 3,330,871.

In accordance with the present invention a composition is provided whichis a homogeneous solution of the acyclic ketone peroxide in a solventsystem, the solution having a flash point of at least about 200° F. Thesolvent system and the individual solvents thereof essentially conformto several characteristics:

I. A MIXTURE OF SOLVENTS WHICH BOILS SMOOTHLY OVER A WIDE RANGE OFTEMPERATURES, PREFERABLY AT LEAST 40° C and which commences to boil at atemperature of at least 175° C, the individual solvents having differingboiling points, preferably between about 200° and 300° C;

ii. a mixture of solvents which has a flash point of at least 200° F,preferably at least 220° F;

iii. a mixture of solvents which has an auto-ignition temperature of atleast 225° C, preferably about 300° to 1000° C;

iv. a mixture of solvents which is a solvent for the ketone peroxide,water and free ketone, and additionally is compatible with the polymersystem to be formed;

v. a mixture of solvents having low volatility;

vi. a mixture of solvents inert to the ketone and hydrogen peroxidereactants and product peroxide;

vii. a mixture of solvents which has a low toxicity;

viii. a mixture of solvents which does not leave a solid residue afterburning, which otherwise would result in afterglow;

ix. the individual solvents must be non-benzenoid;

x. the individual solvents must contain from 2 to 8 acyclic carbonatoms;

xi. the individual solvents should be inert and incapable of degradationunder conditions of formation of the product to materials which maydecompose the product peroxide;

xii. the individual solvents must be non-halogenated, and

xiii. the individual solvents should be incapable of forming amineoxides.

Autoignition temperatures for various solvents and the determinationthereof are described in an article entitled "Autoignition Temperaturesof Organic Chemicals" by Carlos J. Hilads et al., Chemical Engineering,Sept. 4, 1972, pp 75 to 80. Autoignition is the lowest temperature atwhich a material begins to self-heat at a high enough rate to result incombustion.

By utilizing a mixture of solvents of differing boiling points and whichboils smoothly over a wide temperature range, the heat of decompositionof the peroxide is used as heat of vaporization of the solvents andhence flare up due to decomposition of the aliphatic ketone peroxide isnot possible.

The ketone peroxide composition provided in accordance with thisinvention has been found to have excellent end use properties. Forexample, in spray coat applications where polyester gels of only a fewthousandths of an inch thick, typically 10 to 15000, are provided, theproduct of the invention does not give rise to blisters or pin holes, incontrast to many commercially-available ketone peroxide formulations.

Additionally, it has been found that where tapered sections or sectionsof irregular thickness are cured from curable polyester materials inwhich the ketone peroxide composition of this invention is used as thepolymerization initiator, this curing takes place uniformly throughoutthe thickness of the film. This result is of importance in particular inthe fabrication of boats where the use of uneven thickness of polyesterfilm is common.

As a result of this unexpected uniformity of curing, there is lesslaminate stress and lack of excessive localised heat build up. Thestresses and heat build up can cause damage to the expensive molds usedin the boat industry and hence should be avoided. In addition, bubblingcaused by solvents is not observed in the polyester films.

A further result achieved in film formation initiated with thecompositions of the invention is that when the cured article, such as aboat, is removed from the mold, the film is completely cured. In manyconventional systems, the film is not completely cured upon removal fromthe mold.

Compositions in accordance with the present invention have improvedsolubility in diallyl phthalate, as compared to conventionalcommercially-available fire retardent ketone peroxide compositions. Thisproperty is important since diallyl phthalate is widely used as across-linking diluent in spray applications of ketone peroxides.

The acyclic ketone peroxide present in the compositions of the presentinvention is derived from an acyclic ketone of the formula R--CO--R',where R and R' each are straight or branched chain alkyl groups in whichthe total number of carbon atoms in R and R' is from 3 to 6.

Suitble ketones include diethyl ketone, methyl ethyl ketone (MEK),methyl propyl ketone and methyl isobutyl ketone.

The ketone most commonly employed to form ketone peroxides is methylethyl ketone and this particular material is preferred in the presentinvention. The invention will be described hereinafter with particularreference to this ketone.

The compositions of the present invention may be prepared in anyconvenient manner, preferably that described in the parent applicationSer. No. 396,524. In this procedure, which is described in more detailin the parent application, a stoichiometric excess of an acyclic ketoneis reacted with hydrogen peroxide in a homogeneous system provided bythe solvent system mentioned above. The resulting homogeneous solutionis boiled under reduced pressure to strip excess ketone and water fromthe solution to provide the desired product.

BRIEF DESCRIPTION OF DRAWING

The sole FIGURE of the drawing shows a schematic flow sheet of aprocedure for the formation of the compositions of this invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawing, which depicts the formation of ketone peroxidecompositions by the procedure of the parent application Ser. No.396,524, hydrogen peroxide, typically as an aqueous solution thereofcontaining 50 percent H₂ O₂, is fed by line 10 to a reactor 12containing methyl ethyl ketone fed by line 14 and solvent fed by line16. A cation exchange resin in hydrogen ion form, fed by line 18generally in the form of beads and insoluble in the reactants or thesolvent, also is present in the reactor 12. The hydrogen peroxidegenerally is added dropwise to the solution to react with the methylethyl ketone and the reaction may be continued after completion ofaddition of the hydrogen peroxide.

The quantity of methyl ethyl ketone fed by line 14 is at least 1.1 timesthe stoichiometric quantity required to react with the hydrogen peroxidefed by line 10. Typically the amount is at least 1.5 times the weight ofthe hydrogen peroxide solution fed by line 10.

The solvent fed by line 16 is one conforming to the requirements of thesolvent system as outlined above. Each of the solvents may contain from2 to 8 acyclic carbon atoms.

Typical mixtures which may be used to provide the solvent system,especially with methyl ethyl ketone peroxide, include various mixturesof C2 to C6 glycols and C3 to C6 trialkyl phosphates, for example,mixtures of numbers of the following materials:

    ______________________________________                                                   Boiling Point ° C.                                                                  Flast Point ° F.                               Ethylene Glycol                                                                            197.2          240.8                                             Diethylene Glycol                                                                          245.0          290                                               Dipropylene Glycol                                                                         233            330                                               Hexylene Glycol                                                                            198            230                                               Triethyl phosphate                                                                         216            240                                               ______________________________________                                    

Crude ethylene glycol, usually containing quantities of diethyleneglycol and triethylene glycol, may be used in the solvent system fed byline 16. Glycol derivatives, such as ethylene glycol acetate, may beused in the solvent system.

The relative proportions of the solvents, their number, and thedifference between their individual boiling points in the solvent systemmay vary widely and are a matter of choice, provided that the overallcomposition and the individual components conform to the above-describedparameters.

The quantity of solvent fed by line 16 should be at least sufficient tomaintain a homogeneous reaction mixture throughout the addition ofhydrogen peroxide.

The reaction is carried out at as low a temperature as possiblecompatible with speed of reaction. Higher temperatures favourdecomposition of the product, whereas low temperatures below 10° Cresult in long reaction times. The process is carried out at atemperature below about 35° C, preferably between about 20° to 30° C,with reaction times from about 1 to 2 hours.

Following completion of the reaction of the hydrogen peroxide with themethyl ethyl ketone there is obtained a homogeneous solution of solvent,product ketone peroxide, water and unreacted methyl ethyl ketone inadmixture with resin. The admixture is passed by line 20 to a filter 22wherein the solid resin is filtered from the homogeneous solution.Alternatively, the resin may be separated after the next processingstep.

The recovered resin is passed by line 24 to a regenerator 26 prior torecycle of regenerated cation exchange resin to the reactor 12 by line18.

The filtered solution then is passed by line 28 to a stripper 30 whereinthe solution is heated under reduced pressure to remove an azeotrope ofmethyl ethyl ketone and water. While three separate units, namelyreactor 12, filter 22 and stripper 30 are described, this is for ease ofillustration of the process of the invention, and the three operationsmay be carried out in a single vessel.

The stripper 30 generally is maintained under a vacuum in order to lowerthe stripping temperature and hence reduce the danger of decompositionof the ketone peroxide. The temperature of operation of the stripper 30generally is less than about 40° C with the applied vacuum being as highas possible. The excess methyl ethyl ketone and water are removed fromthe homogeneous system in the stripper 30 by line 32. The strippingusually is continued until no further material can be stripped from theproduct, and usually is complete in less than 4 hours, usually about 1hour.

The resulting solution of methyl ethyl ketone peroxide in solvent inline 34 is substantially free from unreacted methyl ethyl ketone andfree water.

It is preferred to provide in the resulting solution of methyl ethylketone in solvent in line 34 a water content less than about 5 percent,preferably from 0 to about 4 percent. The water content of the productmay be determined readily by gas chromatographic techniques. Thistechnique also may be used to determine the free ketone content of theproduct which preferably, is as low as possible. The free ketoneconcentrations of the product should be below a value which willsubstantially lower the flash point of the product, usually below about0.5 percent and, preferably, from 0 to about 0.4 percent.

The product containing the preferred water content conforms to theso-called "Freezing Test". In the Freezing Test, the product is cooledto -50° C and then thawed. To pass this test, the product must remainmobile on lowering the temperature to -50° C and homogeneous on thawing.

When a conventional aliphatic ketone peroxide composition containingsubstantial quantities of water is cooled and subsequently thawed,freezing occurs on lowering the temperature, and a phase separationoccurs on thawing which is extremely difficult to reverse and,additionally, following such phase separation, the composition becomesmore susceptible to explosion.

Further, it has been observed that upon subjectingcommercially-available peroxide compositions of low water content to theFreezing Test, the products solidified between 0° and -5° C.

The product in line 34 has been found to have improved stabilityproperties as compared to conventionally-produced ketone peroxidecompositions, thereby providing a product which may be stored over longperiods without substantial loss of activity and danger of instabilityif stored through cold weather.

The concentration of the ketone peroxide in the product in line 34 maybe in excess of the industry standard of 11 percent active oxygen, inwhich case the product may be diluted with further amounts of solvent,either during the stripping operation or thereafter, to provide therequired active oxygen value.

The active oxygen content of the final composition may vary widely,typically from 0.1 to 13 percent AO, with varying quantities of solventbeing employed, typically from 5 to 90 percent of the composition.

The material in line 32 may be passed to a separator 36 wherein themethyl ethyl ketone is separated and forwarded by line 38 to mix withfurther methyl ethyl ketone fed by line 40 to provide the methyl ethylketone feed in line 14.

By utilizing an excess of methyl ethyl ketone there is realized aneconomic utilization of hydrogen peroxide, and since the excess isrecovered for recycling, hence, there is also economic utilization ofketone.

EXAMPLES

The invention is illustrated further by the following Examples:

EXAMPLE I

A mixture of solvents consisting of 7.38 lbs of triethyl phosphate, 2.62lbs of ethylene glycol, 2.62 lbs of diethylene glycol and 2.62 lbs ofdipropylene glycol was charged to a reaction vessel and 66.5 lbs ofmethyl ethyl ketone was added. 1.36 lbs of Dowex 50 W - X8 cationexchange resin in hydrogen ion form was added to the solution in thereaction vessel.

The mixture of solvents charged to the reaction vessel was found tocommence boiling at 179.5° C and to boil smoothly to dryness over anincreasing temperature range to 224.0° C.

41.6 lbs of 50 percent aqueous solution of hydrogen peroxide was addedslowly with stirring over a 45 minute period, with the temperature beingcontrolled by cooling below about 88° F. The resulting mixture wasallowed to react, with stirring and agitation by nitrogen gas bubbledthrough, for a further 75 minutes.

The liquid in the reaction vessel remained homogeneous throughout thereaction and then was cooled to ambient temperature prior to filtrationof the cation exchange resin therefrom.

Under a vacuum of approximately 27 inches mercury, the filtrate wasstripped of water and unreacted methyl ethyl ketone over a period ofabout 31/2 hours at a rising temperature between 70° and 116° F.

41.2 lbs of stripped material was recovered and 70 lbs of methyl ethylketone peroxide solution was obtained. The product was very difficult toignite, and when ignited burned with a controlled flame until all theliquid was consumed.

In addition, the product was subjected to the Freeze Test and the liquidremained mobile on cooling to -50° C and did not exhibit phaseseparation on cooling and thawing.

The product had an active oxygen content of about 11.5 percent andsamples after storage for 183 days under laboratory conditions in whichthe temperature ranged from 50° to 95° F, mainly 65° to 75° F exhibitedan active oxygen content of 11.2 percent, thereby indicating thestability of the product.

In similar storage tests when exposed to outdoor weather conditions inwhich the temperature ranged from -5° F to 80° F (shade temperature),the active oxygen content of the product after 148 days was 7.4 percent,while comparative samples of Aposet 720 and FR222 had exploded by thattime.

EXAMPLE II

A two-gram sample of the product of Example I was placed in a smallaluminum dish 12.5 mm high by 44 mm diameter. Similar two-gram samplesof commercially-available peroxide compositions known as DNF (Wallaceand Tiernan and formulated in accordance with U.S. Pat. No. 3,330,871)and Aposet 720 (M and T) were placed in similar dishes.

A 3/4 inch flame from a small pilot burner was adjusted to impinge theliquid surface at about a 60° angle. The flame was removed on ignitionof the sample. The times to ignition were recorded for a number ofsamples and the average times are reproduced in the Table I:

                  TABLE I                                                         ______________________________________                                        Example 1          71 secs.                                                   DNF                68 secs.                                                   Aposet 720         25 secs.                                                   ______________________________________                                    

Total burning times varied within samples of each product and a truecomparison in this regard was not possible. The product of Example Iburned mildly until all the peroxide had been consumed. On the otherhand the DNF burned mildly for a short time before burning veryvigorously.

A sample product formed from methyl ethyl ketone and hydrogen peroxidein ethylene glycol burned very readily.

Modifications are possible within the scope of the invention.

What we claim is:
 1. An acyclic ketone peroxide composition having anactive oxygen content of about 0.1 to about 13 percent and a flash pointof at least about 200° F and consisting essentially of a homogeneoussolution of 10 to 95 percent of (a) an acyclic ketone peroxide derivedfrom an acyclic ketone of the formula R--CO--R' where R and R' each arestraight or branched chain alkyl groups in which the total number ofcarbon atoms is from 3 to 6, in 90 to 5 percent of (b) a solvent systemconsisting of a mixture of solvents which boils smoothly over a widerange of temperatures and which commences to boil at a temperature of atleast 175° C, having a flash point of at least 200° F and anautoignition temperature of at least 225° C, said mixture having a lowvolatility, low toxicity and being a solvent for and inert to the ketoneperoxide, said mixture of solvents being incapable of leaving a solidresidue after burning, the individual solvents of said mixture beingnon-benzenoid, nonhalogenated and incapable of forming amine oxides,said individual solvents being selected from C2 to C6 glycols and C3 toC6 trialkyl phosphates and having differing boiling points, saidsolution containing 0 to about 0.5 percent of free acyclic ketone and 0to about 5 percent of water.
 2. The composition of claim 1 having anactive oxygen content of about 11 percent.
 3. The composition of claim 1wherein said acyclic ketone peroxide is methyl ethyl ketone peroxide. 4.The composition of claim 1 wherein said solvent system boils smoothlyover an at least 40° C temperature range.
 5. The composition of claim 1wherein said mixture has a flash point of at least 220° F.
 6. Thecomposition of claim 1 wherein said mixture has an autoignitiontemperature of about 300° to 1000° C.
 7. The composition of claim 1wherein said individual solvents are selected from ethylene glycol,diethylene glycol, dipropylene glycol, hexylene glycol and triethylphosphate.
 8. The composition of claim 1 wherein said individualsolvents have differing boiling points between about 200° and about 300°C.